Wire bonding techniques for interconnecting high temperature die materials such as silicon carbide can be unreliable because the mechanical joints of wire bonds are not designed for use in temperatures exceeding about 150.degree. C. and tend to degrade at temperatures above 200.degree. C.
Another limitation of wire bonding is the fact that high temperature metals such as molybdenum are not compatible with conventional wire bonding. Aluminum has been added to the molybdenum in an attempt to create a wire bondable region, but the bonds remain unreliable at high temperatures.
In one form of high density interconnect (HDI) circuit module, an adhesive-coated polymer film overlay having via openings covers a substrate which can support integrated circuit chips in chip wells. The polymer film provides an insulated layer upon which is deposited a metallization pattern for interconnection of substrate metallization and/or individual circuit chips through the vias. Methods for performing an HDI process using overlays are further described in Eichelberger et al., U.S. Pat. No. 4,783,695, issued Nov. 8, 1988, and in Eichelberger et al., U.S. Pat. No. 4,933,042, issued Jun. 12, 1990. Generally a plurality of polymer film overlays and metallization patterns are used.
This type of HDI circuit module provides efficient use of space and flexibility of interconnection patterns. However, most polymers are not capable of withstanding sustained high temperatures such as 300.degree. C. and above without severe degradation.